Topiramate is a sulfamate substituted monosaccharide which under the trade name TOPAMAX® (Ortho-McNeil Pharmaceutical, Inc., Raritan, N.J., U.S.A.) has been approved for use as an antiepileptic agent, as an adjuvant therapy for patients with partial onset seizures or primary generalized tonic-clonic seizures, and for the prevention of migraine. See generally, Physician's Desk Reference, 60th ed., 2538-2447 (2006); see also, U.S. Pat. No. 4,513,006.
For the treatment of epilepsy, the recommended dose of Topamax® is 400 mg/day in one or multiple doses (Physician's Desk Reference, 60th ed., 2538-2447 (2006)). For adults with epilepsy, treatment is initiated with a dose of 25-50 mg/day, with the dose being titrated in increments of 25-50 mg at weekly intervals to the recommended or effective dose.
Topamax® is an immediate release formulation. Adverse effects associated with the administration of Topamax® include, but are not limited to, somnolence, dizziness, ataxia, speech disorders and related speech problems, psychomotor slowing, abnormal vision, difficulty with memory, paresthesia, diplopia, renal calculi (kidney stones), hepatic failure, pancreatitis, renal tubular acidosis, acute myopia and secondary angle closure glaucoma (Physician's Desk Reference, 60th ed., 2538-2447 (2006)).
Hence, though topiramate has a relatively long half-life of 21 hours in vivo, it has not been prescribed (or formulated) as a single, daily-dose, in part due to severe side-effects that often result with peak plasma levels of the drug when taken in high doses. Instead, Topamax® is typically taken in multiple, “divided” doses, usually twice-daily (“BID”). However, administration of the medicament in this manner is cumbersome and patients can forget to take their medication in a timely manner. What is more, each administration of a dose is associated with a peak in plasma concentrations of the drug, and the fluctuations associated with the peaks and valleys of blood plasma levels of the drug are undesirable. Therefore, there is a need for a formulation of topiramate, which reduces or eliminates the side effects associated with peaking and fluctuating plasma levels of the drug and preferably may be administered in a once-daily regimen.
New, highly soluble and bioavailable forms of topiramate are also needed in order to increase the safety and effectiveness of the drug.
The instant invention addresses these and other needs by providing a modified formulation of topiramate characterized by a sustained, non-pulsatile release of an active ingredient. This invention additionally provides an effective, once-daily dosage form of topiramate or salts thereof, which not only enables an effective single daily dose regimen to improve patient compliance but may also reduce some of the side effects of topiramate compared to the current or higher daily doses of immediate release topiramate formulations.